1. Field of the Invention
An aspect of the present invention relates to at least one of a method for quantitatively analyzing cysteine and cystine and a reagent kit for quantitatively analyzing cysteine and cystine.
2. Description of the Related Art
Methionine, cysteine, and cystine are known as sulfur-containing amino acids that constitute a protein in a living body. These maintain homeostasis through a successive metabolic cycle in a living body. For example, methionine is usually metabolized to cysteine in a living body, and homocysteine produced as an intermediate in this metabolic process is derived into cysteine after formation of cystathionine due to condensation with serine.
Among these, attention is paid to cysteine as a candidate of an index for understanding a cause of metabolic disorder of a sulfur-containing amino acid or an oxidation-reduction-associated disease, and a measurement of a concentration thereof in a living body, for example, in blood is important.
However, because cysteine has a thiol group, this thiol group is oxidized to produce cystine through an oxidation-reduction reaction of a system where cysteine is present. Accordingly, it is difficult to quantify a content of each of cysteine and cystine in a living body accurately.